.onscroll #header{position:fixed;z-index:499;top:0;width:100%;-webkit-transition:top 0.5s ease-in-out;-moz-transition:top 0.5s ease-in-out;-o-transition:top 0.5s ease-in-out;-ms-transition:top 0.5s ease-in-out;transition:top 0.5s ease-in-out;}